An organic light emitting device (referred to as OLED) is a light emitting device using an organic solid semiconductor as a light emitting material, and has a broad application prospect due to its advantages of simple fabricating process, low cost, low power consumption, high luminous brightness, wide range of operating temperature, etc.
A structure of an existing OLED generally comprises an anode layer, a cathode layer, and an organic function layer provided between the anode layer and the cathode layer. The organic function layer comprises a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer and an electron injection layer, which are sequentially provided in a direction from the anode layer to the cathode layer. The hole injection layer is adjacent to the anode layer, and the electron injection layer is adjacent to the cathode layer.
A light emitting mechanism of the OLED is as follows. When an external voltage is applied between the anode layer and the cathode layer, driven by the external voltage, the holes injected from the anode layer enters the light emitting layer through the hole injection layer and the hole transport layer, and the electrons injected from the cathode layer enters the light emitting layer through the electron injection layer and the electron transport layer. The holes and the electrons which have entered the light emitting layer recombine to form excitons in a recombination region, and the excitons emit light by radiative transition, thereby resulting in light-emitting phenomenon, i.e., electroluminescence.
The inventor finds at least the following problems that exist in the prior art. Since the electrons and the holes have different injection rates, i.e., the injection rate of the electrons is larger than that of the holes, amounts of the electrons and the holes injected into the recombination region of the light emitting layer are different from each other, resulting in reduction of a luminous efficiency and a life time of the organic light emitting device.